Power combining is typically done using resonant waveguide cavities or transmission-line feed networks. These approaches, however, have a number of shortcomings that become especially apparent at higher frequencies. First, conductor losses in the waveguide walls or transmission lines tend to increase with frequency, eventually limiting the combining efficiency. Second, these combiners become increasingly difficult to machine as the wavelength gets smaller. Third, in waveguide systems, each device often must be inserted and tuned manually. This is labor-intensive and only practical for a relatively small number of devices.
A known solution is proposed in an article by Kondo et al entitled “Millimeter and Submillimeter Wave Quasi-Optical Oscillataor with Multi-Elements”. The article provides a guide to development of many kinds of oscillators in solid state devices. Solid state devices have many advantages, i.e. small size, light weight and low-voltage power supplies. The article discloses a quasi-optical oscillator having solid-state devices (Gunn Diodes, GaAsMeSFET etc.) mounted in the grooved mirror to obtain a coherent power-combining and frequency locking.
Now referring to FIG. 1, there is illustrated a conventional current approach to an intra-cavity absorption spectrometer (IAS) 100 using the Smith-Purcell effect (electron beam interacting with a grating) and an open resonant chamber in a semi-confocal configuration. The resonator is partitioned into two parts, the lower part being the vacuum chamber 102 containing the electron beam 104 and grating 106 are held at high vacuum ˜10−7 Torr while the upper part being the sample chamber 108 which is held in the range of 10−7 Torr. A thin window 110 separates the high-vacuum region of the electron beam and the grating from the sample chamber. The resonator is formed by a spherical mirror 112 at the top and the grating 106 as shown in FIG. 1. Also, included is a plane mirror 114 upon which the grating 106 resides. This device 100 also requires a large axial magnetic field (˜1 Tesla) to be aligned with the electron beam. In its operation, the device 100 relies upon the THz gain provided by the electron beam interaction with the grating and the resonant chamber to become an oscillator, The major difficulty of this approach is the critical alignment of the electron beam to the magnetic field and the grating. Misalignments cause poor power efficiency and reduced sensitivity. Thus, there is a need in the art to provide an improved Terahertz system to overcome the disadvantages of the prior art.
It is understood that the attached drawings are for the purpose of illustrating the concepts of the invention and may not be to scale.